Organize by Focus?

I homeschool one nine-year-old boy and also work nearly full-time from home. I find that some of his homeschooling is becoming self-directed enough to allow me to work while he completes assignments. I want him to feel free to interrupt me if he has questions. I would like to have a system where tasks could be organized by focus required. Little or no focus tasks could be completed while I am actively engaged in homeschooling (tossing in a load of laundry), medium focus tasks could be completed while he is working independently near me (make appointments, weekly business maintenance tasks like billing), and high focus tasks (large projects or detailed accounting) could be scheduled while he is out playing or at piano and there is little or no chance of interruption. I was wondering if anyone has ever experimented with this and what their set up is? Thanks in advance.